Raman-active phonons in thin a- and c-axis-oriented (YBa2Cu3O7)m(PrBa2Cu3O7)n superlattices

Kyung Min Ham, R. Sooryakumar, I. Takeuchi, Z. Trajanovic, C. Kwon, Qi Li, T. Venkatesan

Research output: Contribution to journalArticle

14 Citations (Scopus)

Abstract

We report on a Raman study that compares the behavior of phonons in several a-axis- and c-axis-oriented superlattices of (YBa2Cu3O7)m(PrBa2Cu3O7)n. The number of individual layers within a superlattice period varied between 1≤m,n≤15. The dependence of the phonon frequencies on m and n shows a significant softening of the vibration associated with the apical oxygen atom [O(4)] in PrBa2Cu3O7 with reductions in the Pr layer thickness (dPr). The modifications to the self-energy of this phonon for both superlattice orientations only occur when dPr25 and therefore establishes the primary importance of the Pr layer thickness in affecting the observed softening. These phonon renormalizations are consistent with charge redistribution in the immediate vicinity (∼10 ) of the interface arising from the unequal Fermi energies associated with the alternating layers. Our study also establishes that the significant differences in the dependence of the superconducting transition temperatures on layer thickness in a- and c-axis-oriented multilayers are not attributable to enhanced interdiffusion between Y and Pr sites or greater loss of oxygen in the a-axis structures. We also find no evidence of a Raman excitation proposed to be a combination B1u-B1g-type vibration recently reported in a c-axis oriented (YBa2Cu3O7)2(PrBa2Cu3O7)1 superlattice.

Original languageEnglish (US)
Pages (from-to)16598-16605
Number of pages8
JournalPhysical Review B
Volume50
Issue number22
DOIs
StatePublished - Jan 1 1994

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superlattices
phonons
softening
vibration
oxygen atoms
transition temperature
energy
oxygen
excitation

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics

Cite this

Ham, K. M., Sooryakumar, R., Takeuchi, I., Trajanovic, Z., Kwon, C., Li, Q., & Venkatesan, T. (1994). Raman-active phonons in thin a- and c-axis-oriented (YBa2Cu3O7)m(PrBa2Cu3O7)n superlattices. Physical Review B, 50(22), 16598-16605. https://doi.org/10.1103/PhysRevB.50.16598
Ham, Kyung Min ; Sooryakumar, R. ; Takeuchi, I. ; Trajanovic, Z. ; Kwon, C. ; Li, Qi ; Venkatesan, T. / Raman-active phonons in thin a- and c-axis-oriented (YBa2Cu3O7)m(PrBa2Cu3O7)n superlattices. In: Physical Review B. 1994 ; Vol. 50, No. 22. pp. 16598-16605.
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abstract = "We report on a Raman study that compares the behavior of phonons in several a-axis- and c-axis-oriented superlattices of (YBa2Cu3O7)m(PrBa2Cu3O7)n. The number of individual layers within a superlattice period varied between 1≤m,n≤15. The dependence of the phonon frequencies on m and n shows a significant softening of the vibration associated with the apical oxygen atom [O(4)] in PrBa2Cu3O7 with reductions in the Pr layer thickness (dPr). The modifications to the self-energy of this phonon for both superlattice orientations only occur when dPr25 and therefore establishes the primary importance of the Pr layer thickness in affecting the observed softening. These phonon renormalizations are consistent with charge redistribution in the immediate vicinity (∼10 ) of the interface arising from the unequal Fermi energies associated with the alternating layers. Our study also establishes that the significant differences in the dependence of the superconducting transition temperatures on layer thickness in a- and c-axis-oriented multilayers are not attributable to enhanced interdiffusion between Y and Pr sites or greater loss of oxygen in the a-axis structures. We also find no evidence of a Raman excitation proposed to be a combination B1u-B1g-type vibration recently reported in a c-axis oriented (YBa2Cu3O7)2(PrBa2Cu3O7)1 superlattice.",
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Ham, KM, Sooryakumar, R, Takeuchi, I, Trajanovic, Z, Kwon, C, Li, Q & Venkatesan, T 1994, 'Raman-active phonons in thin a- and c-axis-oriented (YBa2Cu3O7)m(PrBa2Cu3O7)n superlattices', Physical Review B, vol. 50, no. 22, pp. 16598-16605. https://doi.org/10.1103/PhysRevB.50.16598

Raman-active phonons in thin a- and c-axis-oriented (YBa2Cu3O7)m(PrBa2Cu3O7)n superlattices. / Ham, Kyung Min; Sooryakumar, R.; Takeuchi, I.; Trajanovic, Z.; Kwon, C.; Li, Qi; Venkatesan, T.

In: Physical Review B, Vol. 50, No. 22, 01.01.1994, p. 16598-16605.

Research output: Contribution to journalArticle

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T1 - Raman-active phonons in thin a- and c-axis-oriented (YBa2Cu3O7)m(PrBa2Cu3O7)n superlattices

AU - Ham, Kyung Min

AU - Sooryakumar, R.

AU - Takeuchi, I.

AU - Trajanovic, Z.

AU - Kwon, C.

AU - Li, Qi

AU - Venkatesan, T.

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N2 - We report on a Raman study that compares the behavior of phonons in several a-axis- and c-axis-oriented superlattices of (YBa2Cu3O7)m(PrBa2Cu3O7)n. The number of individual layers within a superlattice period varied between 1≤m,n≤15. The dependence of the phonon frequencies on m and n shows a significant softening of the vibration associated with the apical oxygen atom [O(4)] in PrBa2Cu3O7 with reductions in the Pr layer thickness (dPr). The modifications to the self-energy of this phonon for both superlattice orientations only occur when dPr25 and therefore establishes the primary importance of the Pr layer thickness in affecting the observed softening. These phonon renormalizations are consistent with charge redistribution in the immediate vicinity (∼10 ) of the interface arising from the unequal Fermi energies associated with the alternating layers. Our study also establishes that the significant differences in the dependence of the superconducting transition temperatures on layer thickness in a- and c-axis-oriented multilayers are not attributable to enhanced interdiffusion between Y and Pr sites or greater loss of oxygen in the a-axis structures. We also find no evidence of a Raman excitation proposed to be a combination B1u-B1g-type vibration recently reported in a c-axis oriented (YBa2Cu3O7)2(PrBa2Cu3O7)1 superlattice.

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